Pole foundations on slopes
Pole foundations on slopes
(OP)
I am trying to determine the effects of a light pole foundation located on a slope. When looking at the groundline moment applied to the foundation, how do I account for the slope? What is the angle of the slope for which it can be ignored. I cannot find any guide for determining the appropriate resistant earth pressure due to a slope. Any input or direction would be greatly appreciated.





RE: Pole foundations on slopes
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See FAQ158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"
RE: Pole foundations on slopes
But on a slope, there is a more global slope stability issue where you might have a failure plane through the pile. This would be a concern in that there would be a shearing force introduced through the pile, and/or the pile would be dislocated laterally due to slope failure movements.
RE: Pole foundations on slopes
Good points. But they may or may not apply to this case, since it's in/on a slope. (I would expect good compaction.) Moisture infiltration and frost penetration are problems in limited areas of the U.S., and a sloping site should have good drainage...
However, your argument that is incorrect. Soils around laterally loaded piles (including light/power poles) fail by two mechanisms: wedge failure and flow. Wedge failure occurs near the ground surface - typically (but not always) within 4 pile diameters of the ground surface. Soil flows around the pile at deeper depths, where the wedge failure doesn't occur.
On a slope, the wedge will extend to greater depths in the downslope direction, and to shallower depths in the upslope direction. The real art is in evaluating the effect of the slope on the formation of the soil failure wedge -
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See FAQ158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"
RE: Pole foundations on slopes
RE: Pole foundations on slopes
This approach doesn't work if the "shallow" and/or critical factors of safety for sliding are less than 2. In that case, you will need to do additional work to address the lateral resistance available to the foundation.
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See FAQ158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"